Door Closer Comprising Cam Drive

ABSTRACT

A door closer including a free-swing function, including a door closer housing, an output shaft connected to a door, a piston assembly connected to the output shaft and guided in the door closer housing, a closer spring, a piston rod adapted to connect the piston assembly to the closer spring, a free-swing assembly adapted to enable a translational motion of the piston assembly decoupled from the closer spring when the closer spring is locked, and a hydraulic lock compartment adapted to lock the closer spring. The output shaft is a cam-shaped rolling contour, in particular a cam disc, and the piston assembly includes at least one cam roller abutting on the rolling contour.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2010/007248,filed on 20 Nov. 2010. Priority is claimed on German Application No.: 102009 056 265.6, filed 1 Dec. 2009 and German Application No.: 10 2010013 853.3, filed 1 Apr. 2010, the contents of which are incorporatedhere by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a door closer having a cam drive, and inparticular a door closer having a clearance-free piston assembly.

2. Description of Prior Art

In the state of the art, a differentiation is made between door closersand door drives. In the case of door closers, the door has to be openedmanually by a person. During the opening process, energy is stored, e.g.in a closer spring, and the door closer is able to close the door usingthe stored energy. Contrary thereto, the door drive is an assembly thatautomatically opens and closes the door by an additional auxiliaryenergy, e.g. by a motor or hydraulics . In particular when consideringthe hydraulic circuits in door drives and door closers, significantdifferences can be found. In electro-mechanic door drives, a motor and apump are always, provided, which apply the required hydraulic pressure.The respective pressure chambers are thereby actively charged withhydraulic pressure, such that the opening of the door is effected. Thus,in the door drive, the pressure is generated by the internal components,i.e. motor and pump. Contrary thereto, the pressure chambers in a doorcloser are filled by expansion of the chambers and by suctioning thehydraulic oil from other spaces of the door closer. Herein, the energyfor the closer spring and for the pressure generation is supplied to thedoor closer by opening the door. Consequently, the force and momentcharacteristics as well as the occurring loads are mostly different fora door closer and a door drive. The door drive has to apply the energyfor accelerating the door in an opening direction additionally, whereas,in case of the door closer, the door is accelerated in an openingdirection by the user.

SUMMARY OF THE INVENTION

It is an object of one embodiment the present invention to provide adoor closer which has a very slender structure while being manufacturedat low costs, and which is consequently also applicable as an integrateddoor closer, e.g. in a door frame or a door.

A door closer, in particular a hinge door closer, includes afree-swing-function, comprising a door closer housing, an output shaftto be connected to a door, a piston assembly connected to the outputshaft and guided in the door closer housing, a closer spring, a pistonrod adapted to connect the piston assembly to the closer spring, afree-swing assembly adapted to enable a translational motion of thepiston assembly decoupled from the closer spring when the closer springis locked, and a hydraulic lock compartment adapted to lock the closerspring. Further, the output shaft comprises a cam-shaped rollingcontour, in particular a cam disc, and the piston assembly comprises atleast one cam roller abutting on the rolling contour.

Door closers including sliding rails have prevailed in the last yearsdue to their appearance. In order to simultaneously obtain a comfortableoperation, i.e. a decreasing opening resistance or decreasing openingmoment upon increasing door angle, a cam technology is preferably usedwithin the door closer mechanism of the inventive door closer, in orderto transmit the force between the piston assembly and the output shaft.

Preferably, the door closer including a free-swing-function is used infacilities for handicapped persons, apartments for senior citizens ornursery schools as well as for safeguarding fire protection doors. Incombination with a fire alarm system, the closing of said doors issecured for avoiding a propagation of smoke and fire, without exposingthe users of the door to a constant opening moment of prior art doorclosers. In particular in case of fire protection doors, very strongcloser springs have to be used, such that a safe closing of the door canbe guaranteed also in case of an air draft in the corridors. Thetensioning of such closer springs whenever the door is opened cannot beexpected from children, ill persons, or senior citizens. In this case,the free-swing-function enables that the closer spring is biased onlyonce and remains biased until a possible emergency case. The presentdoor closer can be inserted invisibly into the door leaf or in the doorframe due to its very slender overall width, such that no opticaldrawback occurs and it is protected against demolition by vandalism.

Preferably, the door closer comprises a fluid-tight separating wallarranged in the door closer housing between the piston assembly and thecloser spring, wherein the piston rod passes through the separating wallin a fluid-tight manner. The separating wall is sealed and stationarywith respect to the door closer housing. A slide ring seal is preferablyused between the piston rod and the separating wall. Mostly, a pluralityof seals are combined to achieve a nearly 100% tightness. In case ofonly one seal, a groove ring seal is used as an alternative.

Further, the door closer advantageously comprises a closer springtension piston guided in the door closer housing and abutting on thecloser spring. The piston rod therefore transmits the force from thepiston assembly to the closer spring tension piston. The closer springabuts on the closer spring tension piston.

Preferably, a lock compartment is formed between the separating wall andthe closer spring tension piston. On one side of the separating wall,the piston assembly including the output shaft is arranged. The pistonrod transmits the forces through the separating wall to the other side.On this other side, the lock compartment, the closer spring tensionpiston and the closer spring are arranged.

For the free-swing-function included in the door closer mechanism, thecloser spring, also referred to as energy storing spring, must beretained in a biased position by means of the hydraulic lockcompartment, in order to prevent an immediate closing of the door afterthe manual opening thereof. Since the effective direction of the closerspring is directed to the output shaft via the piston assembly, theadditional closer spring tension piston is preferably used, which pistonacts on the piston assembly via the piston rod. In combination with thepiston rod and the separating wall, the hydraulic lock compartment forhydraulically arresting the closer spring is thus generated. The pistonrod extends through the lock compartment, such that the lock compartmentmay also be referred to as ring space. Based on this structure of theinventive door closer, a decisive difference between the known doordrives and the door closer proposed herein can be well explained. In theknown door drive, an oil volume actively pressurized by a hydraulic pumpis pumped into the pressure chambers, and therewith an energy savingspring is biased through a spring tension piston. Contrary thereto, theproposed door closer provides that the oil volume corresponding to thestroke is displaced from other housing areas into the lock compartmentduring the manual opening process, and the discharge from the lockcompartment is e.g. blocked by a solenoid valve. Thus, in the doorcloser proposed herein, the stored force of the closer spring isabsorbed by the oil pressure and cannot introduce a torque to the outputshaft via the piston assembly.

In a preferred embodiment of the piston assembly, it is provided thatthe piston assembly comprises a damper piston including a first camroller and an opening piston including a second cam roller, wherein theoutput shaft is arranged between the damper piston and the openingpiston. The cam rollers of the damper piston and of the opening pistonhave to be in constant contact with the rolling contour, and thus rollon the rolling contour when the output shaft is rotated. Therewith, acontinuous and clearance-free controlling of the respective rotatingangle of the output shaft is achieved. In case of the very smallstroke-rotary angle-ratios of the cam technology, uncontrolled doormotions would occur upon too much clearance. Therewith, a working strokeis generated for the damper piston and the opening piston. On the longerside of the door closer housing, the closer spring is biased through theopening piston and the piston rod. On the other side thereof, thehydraulically effective damper piston is displaced. By displacing thedamper piston, the hydraulic volume is displaced, such that the doorvelocity during the closing process is controlled or braked byinterposed throttle valves. In combination with the force of the closerspring, a resultant force is generated through the cam geometry of therolling contour, which force generates the opening and closing moment bythe corresponding internal lever arm. In order to design the proposeddoor closer as slender as possible, the opening piston and the damperpiston are preferably arranged in a specific way: The damper piston isdisposed on one side of the output shaft and the opening piston isdisposed on the other side of the output shaft, such that the outputshaft is arranged between these two pistons. Consequently, no directcontact is possible between the opening piston and the damper piston.Said very slender constructional design of the door closer provides thata combination of both functions, biasing the closer spring and dampeningthe closing process, is not directly possible within one component. Therealization of the hydraulic auxiliary function “free-swing” thereforerequires elaborate means on both housing sides, since the functionalareas are arranged separately within the housing. For a comparison: Incase of widely designed floor door closers, only one piston is generallyprovided on the spring side, which simultaneously realizes the closerspring biasing and the damping function. In this case, however, aso-called tab carriage is used, which surrounds the cam contourincluding the two rollers supported therein and secures a constantmonitoring of the cam-roller-contact. Upon use of said plate-carriage,no further considerations are required for securing the clearance-freecontact between the two pistons of the piston assembly and the rollingcontour. However, such a plate-carriage cannot be used in integrated andvery slender constructed door closers, as they are proposed herein. Inaddition, when using a cam technology, it has to be considered thatsmall strokes and thus small volume displacements with simultaneous hightensile force requirements are present, which is a disadvantage comparedto the common rack-and-pinion technologies. Cam door closers thereforerequire sustainable bearings and elaborate hydraulic componentarrangements. In the following, two variants are disclosed, which enablethat the two separated pistons, the opening piston and the damperpiston, always have a clearance-free contact with the rolling contour. Afirst variant uses tie rods and internal clearance compensation springs.The second variant uses pressure springs which engage outside at theopening piston and/or the damper piston.

Preferably, it is provided that the damper piston and the opening pistonare connected via tie rods. Since the opening piston and the damperpiston are arranged on both sides of the output shaft, no direct contactbetween these two pistons is possible. The tie rods enable a connectionof the two pistons, which can be assembled and manufactured easily. Inaddition, the use of a plurality of tie rods results in an efficientprevention of twisting of the two pistons about the longitudinal doorcloser axis.

Further preferred is the use of exactly four tie rods. The four tie rodscan be distributed evenly across the cross-section such that a constanttransmission of force is possible.

Four tie rods enable to encase the diameter of the output shaft fromoutside, on the one hand, and, on the other hand, enable to use theheight of the cam contour without any restrictions in view of loadcapacity. Therewith, a horizontal as well as a vertical symmetry ispossible.

In a particularly preferred embodiment, it is provided that respectivelytwo of the four tie rods are arranged symmetrically with respect to thelongitudinal door closer axis. This means that respectively twodiagonally opposed tie rods have the same distance to the output shaft.In particular, the four tie rods are arranged at corners of an imaginarysquare or rectangle. The output shaft passes through the section pointof the diagonals of said square or rectangle. Due to this arrangement,an absolutely constant transmission of force between the opening pistonand the damper piston, which transmission is directed in parallel withthe longitudinal door closer axis, is possible and a seizure of thepiston assembly is prevented as far as possible.

In a particularly preferred embodiment, it is provided that two tie rodsare arranged above the rolling contour and on both sides of the outputshaft, and two further tie rods are arranged below the rolling contourand on both sides of the output shaft, such that the overall height ofthe rolling contour is arranged between the two upper tie rods and thetwo lower tie rods. Due to the tie rods arranged above and below the camportion or the rolling contour, the complete load capacity of therolling contour can be maintained.

Preferably, it is provided that the piston assembly comprises at leasttwo integrated clearance compensation springs, wherein at least two tierods arranged diagonally to each other are tensile-loaded by theclearance compensation springs, in order to compensate for a clearancebetween the rolling contour and the cam rollers. These twotensile-loaded tie rods provide for a clearance compensation between thecam rollers of the two pistons and the rolling contour, and the othertwo diagonal rods serve to prevent twisting and therewith preventtilting moments and related friction or seizing of the opening pistonand the damper piston.

Therewith, the two pistons assume the smallest possible dimensionbetween the rollers.

Preferably, the clearance compensation springs are arranged in thedamper piston and/or in the opening piston. Therefore, no springsengaging from outside at the piston assembly are required for aclearance compensation between the cam rollers and the rolling contour.Therewith, the piston assembly does not have to be supported againststationary portions of the door closer and can itself secure theclearance compensation due to the internal arrangement of tie rods andclearance compensation springs.

Due to the lacking support on stationary components, no force vector andhence no torque is input into the output shaft. Consequently, the door,when in the free-swing mode, stops exactly at the position desired bythe user. In case only a small torque would be effective in thefree-swing mode, the door would move.

In a preferred manner, the tie rods protrude through the clearancecompensation springs. The clearance compensation springs are formed aspressure springs and press against the ends of the tie rods, such thatthe tie rods are tensile-loaded. The other ends of the clearancecompensation springs are supported against the opening piston or thedamper piston. The ends of the tie rods not being tensile-loaded arerespectively screwed fixedly into the respectively other piston.

As an alternative or in addition to the use of tie rods and clearancecompensation springs, it is preferably provided that a first pressurespring is arranged between the damper piston and the door closerhousing. The first pressure spring is configured for a clearancecompensation between the rolling contour and the first cam roller of thedamper piston. This first pressure spring pressurizes the damper pistonslightly toward the output shaft.

Further, it is preferably provided that a second pressure spring isarranged between the opening piston and the piston rod or between theopening piston and the additional piston or between the opening pistonand the separating wall, wherein the second pressure spring isconfigured for a clearance compensation between the rolling contour andthe second cam roller. This second pressure spring, similar to the firstpressure springs, provides for a clearance compensation between the camroller and the rolling contour. Preferably, the first pressure springand/or the second pressure spring is/are weak enough, such that they donot transmit any torque to the door being perceptible for the user, butonly provide for the clearance compensation in the cam mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is explained in more detail on the basisof the accompanying drawing, in which:

FIG. 1 is an inventive door closer according to a first embodiment;

FIG. 2 is an inventive door closer with closed door at an opening angleof 0° with inactive free-swing for all embodiments;

FIG. 3 is an inventive door closer with opened door at an opening angleof 150° with inactive free-swing for all embodiments;

FIG. 4 is an inventive door closer with closed door at an opening angleof 0° with activated free-swing for all embodiments;

FIG. 5 is an inventive door closer during the opening process withactivated free-swing for all embodiments;

FIG. 6 is a detailed view of the free-swing according to the firstembodiment

FIG. 7 is an inventive door closer according to a second embodiment withan inactive free-swing;

FIG. 8 is the inventive door closer according to the second embodimentwith activated free-swing;

FIG. 9 is a piston assembly of an inventive door closer according to athird embodiment;

FIG. 10 are different sectional views of the piston assembly accordingto the third embodiment;

FIG. 11 is a hydraulic switching symbol for a solenoid valve of aninventive door closer according to a fourth embodiment;

FIG. 12 is a hydraulic switching symbol for a solenoid control valve ofan inventive door closer according to a fifth embodiment;

FIG. 13 is a hydraulic switching symbol for a solenoid control valve ofan inventive door closer according to a sixth embodiment;

FIG. 14 is the hydraulic 3/2-solenoid control valve of the door closeraccording to the fifth embodiment in a de-energized position;

FIG. 15 is the hydraulic 3/2-solenoid control valve of the door closeraccording to the fifth embodiment in an energized position;

FIG. 16 is a detail of FIG. 15;

FIG. 17 is the hydraulic 3/2-solenoid control valve of the door closeraccording to the sixth embodiment in a de-energized position;

FIG. 18 is a detail of FIG. 17, and

FIG. 19 is an inventive door closer according to a seventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the basic structure as well as the hydraulic controland the function of a door closer 41 according to the first embodimentis explained with reference to FIG. 1.

The door closer 41 extends along a longitudinal door closer axis 62. Thedoor closer 41 comprises a door closer housing 42, which in turnincludes a first door closer housing part 43 and a second door closerhousing part 44. In FIG. 1, the various hydraulic lines are shown to beoutside the door closer housing 42. This illustration, however, is onlygiven for facility of inspection. In practice, the hydraulic lines areintegrated into the door closer housing 42. In the following, thestructure of the door closer 41 along its longitudinal door closer axis62 is explained from left to right. A first pressure spring 45 issupported against the door closer housing 42, in particular against afront face of the first door closer housing part 43. The first pressurespring 45 pushes a piston assembly 94. This piston assembly 94 is guidedin the door closer housing 42, in particular in the first door closerhousing part 43. Opposite to the first pressure spring 45, a secondpressure spring 52 abuts against the piston assembly 94. Said secondpressure spring 52 is supported against a separating wall 53, inparticular a housing separating wall.

The separating wall 53 is disposed at the sectional area between thefirst door closer housing part 43 and the second door closer housingpart 44. The separating wall 53 forms a flange for connecting the twohousing parts 43, 44 and simultaneously seals the two housing parts 43,44 against each other. A piston rod 54 passes through the separatingwall 53 along the longitudinal door closer axis 62. The piston rod 54 issealingly guided in the separating wall 53, in particular by a slidering seal. The piston rod 54 is fixedly connected to a closer springtension piston 55. Said closer spring tension piston 55 is guided in thedoor closer housing 42, in particular in the second door closer housingpart 44. The closer spring tension piston 55 is followed by a closerspring 56. The closer spring 56 is supported against the closer springtension piston 55 on one side and against an adjusting unit 57 for thecloser spring biasing on the other side. Adjacent to the adjusting unit57 for the closer spring biasing, a 3/2-solenoid control valve 1, in theembodiment of a cartridge valve, is disposed and integrated into thedoor closer housing 42, in particular in the second door closer housingpart 44.

The piston assembly 94 comprises, on a side thereof facing the firstpressure spring 45, a damper piston 46, and an opening piston 47 on theside facing the piston rod 54. The damper piston 46 comprises a firstcam roller 47 rotatably supported therein. The opening piston 51comprises a second cam roller 50 supported rotatably therein. An outputshaft 48, in the embodiment of a cam shaft, is arranged between thefirst cam roller 47 and the second cam roller 50. The output shaft 48extends along an output axis 85 perpendicular to the longitudinal doorcloser axis 62. Said output shaft 48 transmits the force from the pistonassembly 94 though an arrangement of levers or an arrangement with sliderails to the door as well as from the door to the piston assembly 94.For this purpose, the output shaft 48 comprises a cam-shaped rollingcontour 49.

The first cam roller 47 and the second cam roller 50 roll on thisrolling contour 49. The rolling contour 49 is heart-shaped.

The damper piston 46, the opening piston 51 and the closer springtension piston 55 are sealingly guided within the door closer housing 42and, for this purpose, preferably comprise seals or sealing flanges attheir circumference. Due to this sealed guiding of the pistons,different spaces or chambers are generated in the door closer housing42, which are connected to each other via various hydraulic lines. Saidchambers or spaces are, according to the structure shown in FIG. 1,again explained from left to right along the longitudinal door closeraxis 62: A closure damping compartment 58 is formed, defined by the leftend face of the door closer housing 42, in particular the first doorcloser housing part 43, and the damper piston 46. A piston assemblyinner space 59 is disposed between the damper piston 46 and the openingpiston 51, also referred to as cam shaft space. The piston assemblyinner space 59 is on both sides sealed by the damper piston 46 and theopening piston 51 and is always maintained at a tank pressure level. Anopening damping compartment 60 is disposed between the opening piston 51and the separating wall 53. On the other side of the separating wall 53,the lock compartment 61 is arranged between the separating wall 53 andthe closer spring tension piston 55. The lock compartment 61 is definedby the separating wall 53, the wall of the second door closer housingpart 44 and the closer spring tension piston 55. In addition, the doorcloser 41 comprises a tank compartment 31. The tank compartment 31 isarranged between the closure spring tension piston 55 and the solenoidcontrol valve 1 and accommodates the closer spring 56 and the adjustingunit 57. Based on FIGS. 11 to 18, the specific design of the solenoidcontrol valve 1 is explained later on. In this context, also thespecific constructive design of a preferred tank compartment 31 will beexplained. In particular, also a closer spring accommodating space 92and/or the piston assembly inner space 59 can be used as a tank byunthrottled connections to the tank compartment 31.

The door closer 41 comprises a first hydraulic line, embodied aspressure line P, a second hydraulic line, embodied as operating line A,and a third hydraulic line, embodied as tank line T. The three hydrauliclines extend in parallel with the longitudinal door closer axis 62 inthe door closer housing 42. The three hydraulic lines are connected tothe various chambers or spaces in the door closer 41 through shortchannels which extend radially/vertically with respect to thelongitudinal door closer axis 62. FIG. 1 shows the hydraulic lines onlyschematically. In practice, the hydraulic lines are integrated into thedoor closer housing 42. The pressure line P extends from the lockcompartment 61 to the solenoid control valve 1 directly and withoutbeing throttled. The operating line A extends from the closure damperspace 58 to the solenoid control valve 1 directly and without beingthrottled. The solenoid control valve 1 is further connected to the tankline T. The designation “direct and without being throttled” means thatno separate throttles are provided in the lines. Nevertheless, thepressure can be slightly throttled by possible filters or dynamicpressure differences.

The opening damping compartment 60 is connected to the tank line Tthrough a first throttled connection 78. For this purpose, a firstthrottle valve 65 is used. In addition, a first unthrottled connection77 exists between the opening damping compartment 60 and the tank lineT. The opening of the opening damping compartment 60 into the firstunthrottled connection 77 lies nearer to the output shaft 48 than theopening of the opening damping compartment 60 into the first throttledconnection 78. Therewith, the unthrottled connection 77 can be closed bythe opening piston 51 when a specific opening angle of the door isreached.

The closure damping compartment 58 is connected to the tank line Tthrough a second throttled connection 75 arranged at the front face ofthe first door closer housing part 43. For this purpose, a secondthrottle valve 63 is used. In addition, a third throttled connection 76is provided in the circumferential surface of the door closer housing 42between the closure damping compartment 58 and the tank line T,including a third throttle valve 64. The piston assembly inner space 59is connected to the tank line T in an unthrottled manner by at least oneradial channel. A filter 31 is depicted in the tank line T. Herein, theposition of the filter 31 is only exemplary. For example, the filter 31can also be integrated into the solenoid valve 1. Preferably, furtherfilters 31 can be arranged in the other hydraulic lines.

In the damper piston 46, a first check valve 66 is installed. This checkvalve locks toward the piston assembly inner space 59. A second checkvalve 67 is installed in the closer piston 51 that also locks toward thepiston assembly inner space 59. A third check valve 68 is provided inthe closer spring tension piston 55. This check valve enables ahydraulic flow toward the lock compartment 61 and a locking toward thetank compartment 31. A forth check valve 69 is provided between the tankcompartment 31 and the tank line T. Said check valve is spring-loadedand locks toward the tank line T. With the first, second and third checkvalves 66, 67 and 68, the closure damping compartment 58, the openingdamping compartment 60 and the lock compartment 61 can always be filledwith hydraulic oil from the tank volume upon expansion.

A free-swing assembly is formed between the piston rod 54 and theopening piston 51.

The constructive design of this free-swing assembly is explained in moredetail in FIG. 6. At first, however, the functions and motions of thedoor closer 41 are explained in more detail with reference to FIGS. 2 to5. The functions and motions of the door closer 41 according to FIGS. 2to 5 are applicable for all embodiments proposed herein. FIG. 2 showsthe door closer 41 at an angle position of 0° with a released closerspring. FIG. 2 therewith shows the starting position of the door closer41. FIG. 3 shows the door closer during opening at an angle position of150° of the output shaft 48. The door is opened by a person. Due tothis, the output shaft 48, which is connected to the door frame via anarrangement of levers, rotates. The force is transmitted through therolling contour 49 to the cam rollers 47, 50. This results in atranslational motion of the piston assembly 94 to the right. Togetherwith the piston assembly 94, also the piston rod 54 and therewith thecloser spring tension piston 55 are moved to the right. Consequently,the closer spring 56 is biased. During this opening process, thepressure line P is closed by the solenoid control valve 1. Hydraulicfluid is pushed through the third check valve 68 into the lockcompartment 61. The opening process shown in FIG. 3 serves to tensionthe closer spring 56. After tensioning the closer spring 56 and bykeeping the pressure line P closed, the free-swing-function of the doorcloser 41 is active. FIG. 4 shows the door closer 41 again in a closedposition with a door angle of 0°. As is easily discernible, the closerspring 56 remains in the tensioned position, since the lock compartment61 is still filled with hydraulic oil. Together with the closer springtension piston 55, also the piston rod 54 remains unmovable. Due to thefree-swing assembly, the piston assembly 94 lifts off the piston rod 54through the backturn of the output shaft 48 upon a closing motionoperated manually at the door. Herein, the piston assembly 94 can freelymove together with the door. Merely a slight force is transmittedthrough the two pressure springs 45, 52 to the piston assembly 94, suchthat a constant and clearance-free contact of the piston assembly 94 tothe output shaft 48 and the cam contour 49, respectively, is secured bythe cam rollers 47 and 50. As shown in FIG. 5, the closer spring 56remains in its tensioned and arrested position during thefree-swing-function. Meanwhile, the door is freely movable without anytorque.

FIG. 6 shows a detailed view of the free-swing according to the firstembodiment. The free-swing assembly is here embodied as asliding-coupling. The two essential components of this free-swingassembly are the first front face 74 and the second front face 72. Thefirst front face 74 is parallel to the second front face 72. Both frontfaces 74, 72 are positioned vertically with respect to the longitudinaldoor closer axis 62. The first front face 74 is a front face of thepiston rod 54. The second front face 72 is located at the pistonassembly 94, in particular at the opening piston 51. In the embodimentshown in FIG. 6, a pocket 71 is included in the opening piston 51. Apart of the piston rod 54 engages with this pocket 71 and is guidedtherein along the piston guide 73. The second front face 72 is formed asa bottom of the pocket 71. The two front faces 74, 72 are thus arrangedopposite to each other in the pocket 71 and can mutually lift off incase of a free-swing.

FIGS. 7 and 8 show a door closer 41 according to a second embodiment.Identical components or components identical in function are designatedwith identical reference numerals in all embodiments. FIG. 7 shows adoor closer 41 during biasing of the closer spring 56. In FIG. 8, thelock compartment 61 is hydraulically blocked through the pressure lineP. Consequently, the closer spring tension piston 55 and the closerspring 56 remain in their tensed positions. The piston assembly 94 andthe door are freely swingable.

Apart from the difference described in the following, the secondembodiment corresponds to the first embodiment. Contrary to the firstembodiment, an additional piston 95 is arranged between the separatingwall 53 and the piston assembly 94, in particular the opening piston 51,in the second embodiment. The additional piston 95 is fixedly connectedto the piston rod 54 for transmitting a translational motion. The firstfront face 74 is formed frontally at the additional piston 95. Theadditional piston 95 comprises a passage, such that the area between theadditional piston 95 and the piston assembly 94 as well as the areabetween the additional piston 95 and the separating wall 53 form theopening damping compartment 60. A further difference between the firstembodiment and the second embodiment is that, in the second embodiment,the piston rod 54 is connected pivotally to the additional piston 95 andthe closer spring tension piston 55. The connection between the pistonrod 54 and the additional piston 95 is pivotal about a first axis 79.The connection between the piston rod 54 and the closer spring tensionpiston 55 is pivotal about a second axis 80. Both axes 79, 80 arepositioned vertically with respect to the longitudinal door closer axis62. In addition, the first axis 79 is positioned vertically with respectto the second axis 80. Further, the axis 80 is positioned verticallywith respect to the longitudinal door closer axis 62. Said pivotalconnection of the piston rod 54 prevents a seizing of the assembly incase forces occur, which do not extend in parallel with the longitudinaldoor closer axis 62.

FIGS. 9 and 10 show a piston assembly 94 of the door closer 41 accordingto a third embodiment. Identical components or components identical infunction are designated with identical reference numerals in allembodiments. The piston assembly 94 of the third embodiment canpreferably be used in the door closers 41 according to all embodimentsproposed herein.

The piston assembly 94 proposed in FIGS. 9 and 10 replaces the pistonassembly 94 of FIGS. 1 to 7, in particular the damper piston 46including the first cam disc 47 and the opening piston 51 including thesecond cam disc 50. The output shaft 48 remains unchanged. Due to theuse of the piston assembly 94 according to The third embodiment, thefirst pressure spring 45 and the second pressure spring 52 are notrequired, however, can be used in addition.

FIG. 9 shows the piston assembly 94, wherein the damper piston 46 andthe opening piston 51 are connected by a first tie rod 81, a second tierod 82, a third tie rod 83 and a forth tie rod 84. The four tie rods 81to 84 are arranged in parallel with the longitudinal door closer axis62. In addition, the four tie rods 81 to 84 are arranged at four cornersof a square or rectangle to be considered for the purpose of explanationonly. The output axis 85 of the output shaft 48 passes through thesection point of the diagonals of said square or rectangle. Due to thisspecific arrangement of the four tie rods 81 to 85, the complete height91 (see FIG. 10) of the rolling contour 49 can be disposed between thetwo upper tie rods 81, 82 and the two lower tie rods 83, 84. The height91 of the rolling contour 49 is defined in direction of the output axis85. The rolling contour 49 does not need any recesses for the tie rods81 to 84 and may therefore be loaded optimally.

The four tie rods 81 to 84 are respectively connected to the openingpiston 51 by threads 87. At the other ends thereof, the four tie rods 81to 84 protrude into through-holes of the damper piston 46. Here, theends of the tie rods 81 to 84 are respectively screwed by a springtension nut 88. The first tie rod 81 and the third tie rod 83 beingarranged diagonally to the first tie rod 81 are respectivelytensile-loaded by an integrated clearance compensation spring 86. Theintegrated clearance compensation springs 86 are fit on the first tierod 81 and the third tie rod 83 and are located in the damper piston 46.A first end of the clearance compensation springs 86 facing away fromthe output shaft 48 is supported against the spring tension nut 88 whichis screwed to the respective tie rods 81, 83. A second end of therespective clearance compensation springs 86 facing the output shaft 48is supported against a shoulder 93 (see FIG. 10) which is formed in thedamper piston 46. Due to this specific arrangement, the clearancecompensation springs 86, which are embodied as pressure springs, mayload the first and second tie rods 81, 83 with tension.

In addition, FIG. 9 shows a first sealing flange 89 at the damper piston46, which seals the damper piston 46 with respect to the door closerhousing 42, in particular with respect to the closure dampingcompartment 58. In a similar manner, the opening piston 51 is sealedwith respect to the door closer housing 42 by means of a second sealingflange 90. The second sealing flange 90 is formed as a supportingshoulder for a piston seal. The opening piston 51 is formed integrallywith the second sealing flange 90. These two sealing flanges 89, 90 areused in the piston assemblies 94 of all embodiments.

The integrated clearance compensation springs 86 are arranged within apiston, preferably within the damper piston 46. The integrated clearancecompensation springs 86, in combination with their associated tie rods,provide that the smallest possible distance between the two cam rollers47 and 50 is maintained, which are spaced by the rolling contour 49,wherein the cam rollers 47 and 50 abut on the rolling contour 49 withouta clearance.

The integrated clearance compensation springs 86 are to be configuredsuch that the friction of the components within the piston assembly 94as well as the friction of the sealing flanges 89 and 90 with respect tothe portion of the first door closer housing part is overcome, sinceotherwise the cam rollers 47 and 50 would lift off from the rollingcontour 49 upon a stroke motion of the piston assembly 94 in thefree-swing-mode.

Due to this arrangement of the integrated clearance compensation springs86, no counter-bearing with respect to the components of the door closeroutside the piston assembly 94 is generated, such that no forces aretransmitted to the rolling contour 49 and, consequently, no undesiredtorque is transmitted to the output shaft 48.

FIG. 10 shows three sectional views of the piston assembly 94 accordingto the third embodiment. In section B-B, it is discernible that hereagain the pocket 71 is formed in the opening piston 51. At the bottom ofthis pocket, there is the second front face 72. The piston rod 54engages with this pocket 71, such that the free-swing-function isguaranteed.

The embodiments proposed up to now show two basic possibilities for aclearance compensation between the cam rollers 47, 50 and the rollingcontour 49. In the first two embodiments, the damper piston 46 ispressure-loaded by the first pressure spring 45 slightly toward theoutput shaft 48. The opening piston 51 is pressure-loaded by the secondpressure spring 52 slightly toward the output shaft 48. This secures aconstant contact between the cam rollers 47, 50 and the rolling contour49. An alternative is disclosed in the third embodiment. In this case,the clearance compensation is integrated into the piston assembly 94.The damper piston 46 and the opening piston 51 are always slightlyconstricted by the tie rods 81 to 84 and the integrated clearancecompensation springs 89, such that the two cam rollers 47, 50 alwaysabut on the rolling contour 49. In this context, it is particularlyadvantageous that no moment acts on the output shaft 48 and therewiththe door stands still in any possible position during thefree-swing-mode. The symmetric and diagonal arrangement of the four tierods 81 to 84 provides for an absolutely constant force transmission andtherewith prevents any canting. For this purpose, the two used clearancecompensation springs 46 are arranged at two tie rods 81, 83 beingdiagonal to each other. As an alternative, one clearance compensationspring 86 could be provided for each of the tie rods 81 to 84. Ofcourse, the clearance compensation springs 86 can preferably be arrangedin total or partially also in the opening piston 51. in addition, thetie rods 81 to 84 prevent a twisting of the damper piston 46 and theopening piston 51 with respect to one another.

Further, the piston assembly 94 according to the third embodiment canalso preferably be used together with the first pressure spring 45and/or the second pressure spring 52. A specific application is e.g.given in case of very heavy fire protection doors. The closing forcerequired in case of a fire requires very strong closer springs 56. Forthe everyday use of the door, it would be desirable that the closerspring 56 always remains biased and closes the door e.g. in case of afire. Nevertheless, there exists the need for a smooth-running andautomatically closing door, wherein said easy closing should occur aftereach use. Therefore, it is preferable that each of the door closers 41proposed herein comprises the second pressure spring 52 as an“additional closer spring”, embodied e.g. according to EN1 or EN2,wherein said additional closer spring/second pressure spring 52 is muchmore weaker than the closer spring 56. The second pressure spring 52 inthis embodiment therewith always loads the piston assembly 94, inparticular the opening piston 51, in the closing direction, even when infree-swing-mode and upon a blocked closer spring 56, such that the doorcloses, at least if the resistance is not too large, automatically, alsoduring the free-swing-mode. Nevertheless, the user does not have totension the large closer spring 56 upon each opening process, but onlythe much smaller second pressure spring 52. In particular in thisembodiment, the piston assembly 94 according to FIGS. 9 and 10 accordingto the third embodiment can be preferably combined with the secondpressure spring 52.

FIGS. 11, 12 and 13 show a fourth, fifth and sixth embodiment for a doorcloser 41, wherein the switching symbol for the solenoid control valve 1is respectively shown. FIG. 12 illustrating the fifth embodiment showsthe preferred variant.

The fourth embodiment according to FIG. 11 shows a very simpleembodiment, in which the operating line A to the closure dampingcompartment 58 is omitted in such door closer 41. The solenoid controlvalve 1 here only controls a connection of the pressure line P from thelock compartment 61 to the tank line T. The pressure line P canalternatively be open or closed, such that the free-swing is selectivelyde-activated or activated.

FIG. 12 shows the switching symbol for the fifth embodiment. Herein, thepressure line P is connected to the tank line T in a de-energized stateof the solenoid control valve 1, shown on the left side. The operatingline A is blocked. The switching position on the right shows theenergized state of the solenoid control valve 1. Herein, the pressureline P and thus the lock compartment 61, and consequently also thecloser spring 56, are locked. The closure damping compartment 58 isshorted to the tank via the operating line A.

FIG. 13 shows the switching symbol for the sixth embodiment. Accordingto the left depiction, the pressure line P is connected to the operatingline A in a de-energized state. In the energized state according to theright depiction, the pressure line P and thus the lock compartment 61are blocked. The operating line A and, consequently, the closure dampingcompartment 58 are shorted to the tank line T.

FIGS. 14 to 16 show the constructive design of the solenoid controlvalve 1 of the door closer 41 according to the fifth embodiment.Subsequently, a constructive design of the solenoid control valve 1 fora door closer 41 according to the sixth embodiment is explained based onFIGS. 17 and 18.

Based on FIG. 14, the switching position according to FIG. 12, leftside, is shown. FIGS. 15 and 16 show the switching position according toFIG. 12, right side.

FIG. 14 shows a sectional view of the hydraulic 3/2-solenoid controlvalve in a de-energized state. The hydraulic 3/2-solenoid control valve1 comprises a valve housing 2, a valve chamber 3 integrated into thevalve housing 2, a solenoid 4 and a valve spindle 5. The valve spindle 5moves in a longitudinal direction along a valve axis 38.

The valve chamber 3 comprises a first valve seat bore 6 as a connectionfrom the pressure line P to the valve chamber 3 and a second valve seatbore 7 as a connection from the operating line A to the valve chamber 3.Further, a free aperture 8 to the tank line T is formed at the valvechamber 3. The first valve seat bore 6 is located directly opposite tothe second valve seat bore 7. The free aperture 8 is also formed as aborehole, wherein the borehole of the free aperture 8 is arrangedvertically with respect to the first valve seat bore 6 and the secondvalve seat bore 7. In addition, a diameter of the first valve seat bore6 is considerably smaller than a diameter of the second valve seat bore7.

The valve spindle 5 has a split structure and comprises a first part 12and a second part 13 being screwed into the first part 12 and thusfixedly connected to the first part 12. The second part 13 extends fromthe interior of the valve chamber 3 through the second valve seat bore 7toward the solenoid 4. The first part 12 is disposed completely outsidethe valve chamber 3.

The second part 13 of the valve spindle 5 comprises a first sealingsurface, embodied as a convex surface 9 (see in particular FIG. 16) on aside thereof facing the valve seat bore 6. Said convex surface 9 isformed by a ball 10. The ball 10 in turn is embedded into a face siderecess of the valve spindle 5, in particular of the second part 13. Inaddition, a shoulder is formed at the valve spindle 5, in particular atthe second part 13. A valve pressure spring 14 is supported on saidshoulder. The convex surface 9 is arranged within said valve pressurespring 14. The valve pressure spring 14 is further supported at thefront face of the first valve seat bore 6. Said front face can also bereferred to as sealing surface or lateral surface of the first valveseat bore 6. Due to this arrangement of the valve pressure spring 14,the valve spindle 5 is loaded toward the solenoid 4. In a de-energizedstate, this results in an opening of the first valve seat bore 6.

At the second valve seat bore 7, the valve spindle 5, in particular thesecond part 13, comprises a second sealing surface, embodied as a conering surface 11, within the valve chamber 3. Said cone ring surface 11is formed about the complete circumference of the valve spindle 5. In ade-energized state of the solenoid 4, said cone ring surface 11 ispushed onto the second valve seat bore 7 and therewith seals theoperating line A with respect to the valve chamber 3.

The solenoid 4 comprises a coil 16, an armature 17 and a pole core 18.The coil 16 is wound about the armature 17 and the pole core 18. Thearmature 17 and the pole core 18 are arranged in series along thelongitudinal valve axis 38. In the pole core 18, a borehole is formedalong the longitudinal valve axis 38. Said borehole forms a linear guide19 for at least a portion of the valve spindle 5, in particular aportion of the first part 12 of the valve spindle 5. In an energizedstate, a gap 20 being as small as possible exists between the pole core18 and the armature 17. In the de-energized state, said gap 20 islarger. The solenoid 4 further comprises a connecting line or voltagesupply 21 for connecting a control unit to the hydraulic 3/2-solenoidvalve 1. The armature 17 and the pole core 18 are embedded into a sleeve23. Further, an insulation 24 exists between the sleeve 23 and the coil16.

The pole core 18 and the armature 17 are arranged in a so-calledarmature space 22. Said armature space 22 is located within the sleeve23. The operating line A is sealed with respect to said armature space22 by a specific seal, in particular a groove ring seal 25. Said groovering seal 25 is arranged between the valve spindle 5, in particular thefirst part 12, and the pole core 18. A connection channel 15 extendswithin the valve spindle 5. Said connection channel 15 connects thearmature space 22 to the valve chamber 3. Since the valve chamber 3 isalways freely connected to the tank line T, also the armature space 22is always pressureless. The connection channel 15 is formed by alongitudinal borehole along the longitudinal valve axis 38 in the valvespindle 5 as well as by boreholes being vertical with respect to thelongitudinal valve axis 38 from the surface of the valve spindle 5 tothe longitudinally extending borehole. Due to the split structure of thevalve spindle 5, in particular, the longitudinal borehole can be formedalong the longitudinal valve axis 38 inside the valve spindle 5.

The valve housing 2 comprises a base housing component 26, a first valvechamber insert 27 and a second valve chamber insert 28. The first valvechamber insert 27 and the second valve chamber insert 28 together formthe valve chamber 3. The hydraulic 3/2-solenoid control valve 1 isstructured and assembled as follows: An annular extension 29 is disposedat the solenoid 4. A part of the second valve chamber insert 28 isembedded into said extension 29. The second valve chamber insert 28 inturn accommodates the first valve chamber insert 27. The alreadymentioned sleeve 23 of the solenoid 4 extends to the second valvechamber insert 28 and is connected thereto. The complete unit consistingof solenoid 4, second valve chamber insert 28 and first valve chamberinsert 27 is screwed into the base housing component 26. For thispurpose, an internal thread is formed at the base housing component 26,and a corresponding external thread is formed at the extension 29 of thesolenoid 4. The individual housing components are sealed against eachother.

In addition, the housing 2 comprises a cap 30. The cap 30 encases thesolenoid 4 and sits on the base housing component 26.

A drilled insert 35 is formed inside the first valve chamber insert 27.The first valve seat bore 6 is formed in said drilled insert 35. Theinsert 35 and the valve chamber insert 27 are preferably formed as onepiece. In addition, a filter 36 is arranged in the first valve chamberinsert 27. Said filter 36 is disposed outside the valve chamber 3 and inthe pressure line P.

In addition, a volume compensation unit 37 including the tankcompartment 31 is integrated inside the base housing component 26. Saidvolume compensation unit 37 including the tank compartment 31 comprisesa volume compensation piston 32, a compensation spring/lengthcompensation spring 33 and a bearing 35 for the compensation spring 33.The tank compartment 31 is connected to the tank line T. The volumecompensation piston 32 defines a wall of the tank compartment 31. Thepiston 32 is slightly spring-loaded by the compensation spring 33. Thecompensation spring 33 is supported against the volume compensationpiston 32 on one side thereof and against the spring bearing 34 on theother side thereof. The front face of the spring bearing 34 is screwedinto the base housing component 26.

The hydraulic 3/2-solenoid control valve 1 is constructed substantiallyrotation-symmetrically with respect to the longitudinal valve axis 38.The pressure lines P, the operating lines A and the tank lines T deviatefrom said rotation symmetry. The pressure line P and the operating lineA end at respectively at least one position on the circumferentialsurface of the base housing component 26. At this position, ringchannels 39 are formed. Said ring channels 39 are sealed with O-ringseals 40, when the 3/2-solenoid control valve 1, embodied as a cartridgevalve, is inserted into a corresponding receptacle.

FIG. 15 shows the hydraulic 3/2-solenoid control valve 1 according tothe embodiment in the energized state. Herein, it is clearly visiblethat the valve spindle 5 was moved to the left compared to theillustration of FIG. 14. Consequently, the operating line A is directlyconnected to the valve chamber 3 and thus with the tank line T and thetank compartment 31 via the second valve seat bore 7. The pressure lineP is blocked by the seating of the ball 10 in the first valve seat bore6 and is therefore not connected to the valve chamber 3.

FIG. 16 shows a detail of FIG. 15. Based on this illustration,particularly the differential-area-ratio can be explained. It shall benoted that said differential-area-ratio is used upon a closed secondvalve seat bore 7 and thus in the de-energized valve position shown inFIG. 14. As shown in FIG. 16, the valve spindle 5 comprises a sealingdiameter D1 at the groove ring seal 25. The second valve seat bore 7 hasan inner diameter D2. In a region between the groove ring seal 25 andthe second valve seat bore 7, the valve spindle 5 has a smallestdiameter D3. When the second valve seat bore 7 is closed, the pressurein the operating line A acts on the following surfaces of the valvespindle 5: The first surface is calculated by (D2 ²/4*π)−(D3 ^(2/)4*π).The second surface is calculated by (D1 ²4*π)−(D3 ²/4*π). Due to thefact that the first surface is smaller than the second surface theoperating pressure acts to the right in the shown illustration when thesecond valve seat bore 7 is closed. The valve pressure spring 14 issupported and the cone surface 11 is pulled into the second valve seatbore 7.

Based on the fifth embodiment, it was explained how a hydraulic3/2-solenoid control valve 1, in particular with a cartridge design, canbe formed for an operation free of leakage oil. In the de-energizedswitching position, shown in FIG. 14, the side of the valve spindle 5formed as the cone surface 11 is pushed into the second valve seat bore7 of the operating line by the pressure spring 14 and therewith blocksthe connection of said line with respect to the tank in an oil-tightmanner. On the magnet side, the valve spindle 5 is radially formed witha groove ring seal 25 with respect to the armature space 22. The sealingdiameter D1 of the valve spindle 5 toward the armature space 22 islarger than the second valve seat bore 7. Therewith, there results adefined area ratio between the cone seat and the sealing diameter D1 ofthe armature space 22. If the operating line A is pressurized, adifferential force is generated through the area ratio between theoperating line and the sealed armature space 22, which force pulls thevalve spindle 5 toward the solenoid 4 and acts in addition to theelastic force against the second valve seat bore 7. The sealing effectincreases with increasing pressure in the operating line A. The solenoid4 is preferably configured such that a switching against the elasticforce plus differential force is prevented. In this position, thepressure line P and the tank line T are connected to each other.

In the energized switching position according to FIG. 16, the operatingline A is pressureless, wherein the valve spindle 5 seals, with its ball10, the pressure line P in an oil-tight manner against the elasticforce. A consumer connected through the pressure line P, e.g. the lockcompartment 61, can now be effectively sealed until the rated operatingpressure is reached. Said operating pressure is dependent on themagnetic force. In this switching position, the operating line A isconnected to the tank line T without pressure. Therewith, no pressure oronly a small dynamic pressure can build up in the operating line A.

The embodiments of the proposed 3/2-solenoid control valve areapplicable according to embodiment the invention also for other valvedesigns, independent from the cartridge design and independent of thenumber of lines and/or switching positions. In particular a combinationof ball seat and cone seat in a valve, in particular on a valve spindle,and/or the differential-area-ratio are applicable for other valvesaccording to the invention.

Based on FIGS. 17 and 18, the constructive design of the solenoidcontrol valve 1 of the door closer according to the sixth embodiment isnow explained in more detail. Both figures show the de-energizedswitching position with an open pressure line P, as shown schematicallyon the left side of FIG. 13. Identical components or componentsidentical in function are designated with identical reference numeralsin all embodiments. In particular, the solenoid control valve 1 used inthe sixth embodiment corresponds to the solenoid control valve 1 used inthe fifth embodiment, except for the differences described in thefollowing.

As shown in FIGS. 17 and 18, the tank line T and the operating line Aare interchanged in the sixth embodiment compared to the fifthembodiment. This means that the operating line A is always connected tothe valve chamber 3 through the free aperture 8. The connection betweenthe valve chamber 3 and the tank line T is controlled by the secondvalve seat bore 7 and the cone ring surface 11. in addition, the valvespindle 5 of the sixth embodiment is formed in one piece. Further, thepath for the pressure compensation between the armature space 22 and thetank line T is shorter in the solenoid control valve 1 according to thesixth embodiment. Herein, the connection 15 is formed as a simple flatsurface between the armature space 22 and the tank line T. No boreholesare required in the valve spindle 5. The connection 15 is formed as aflat surface on the valve spindle 5 or by forming the valve spindle 5 asa polygon.

In addition, the valve housing 2 in the solenoid valve 1 according tothe sixth embodiment is designed somewhat simpler. The valve chamber 3is no longer structured in two parts including a first valve chamberinsert 27 and a second valve chamber insert 28. Rather, only one valvechamber insert 27 is used in this embodiment.

The solenoid valves according to the fourth, fifth and sixth embodimentsof the door closer 41 can preferably be used in all embodiments of thedoor closer 41 proposed herein.

FIG. 19 shows a door closer according to a seventh embodiment. Identicalcomponents or components identical in function are designated withidentical reference numerals in all embodiments. The assembly foravoiding a so-called rebound of the closer spring tension piston 55proposed in the seventh embodiment can preferably be used in allembodiments of the door closer 41 proposed herein.

FIG. 19 shows an embodiment of the third check valve 68 in the closerspring tension piston 55 as a spring-loaded check valve. The spaceinside the door closer housing 42, in particular inside the second doorcloser housing part 44, in which the closer spring 56 is arranged, isherein referred to as closer spring accommodating space 92. Said closerspring accommodating space 92 is a space which becomes smaller duringthe opening process of the door, since the closer spring tension piston55 moves to the right. In addition, FIG. 19 shows the fourth check valve69 also as a spring-loaded check valve. The third check valve locks thehydraulic flow from the lock compartment 61 into the closer springaccommodating space 92. The fourth check valve locks the hydraulic flowfrom the closer spring accommodating space 92 into the tank line T.

The closer spring accommodating space 92 and the tank compartment 31herein are a space with hydraulic interconnection. The supporting discfor the spring 56 shown in the adjusting unit 57 is no hydraulicseparating wall.

When pressure builds up in the lock compartment 61, all elastic membersarranged therein, e.g. seals, residue air or also the hydraulic fluid,are compressed accordingly, which results in an undesired loss ofvolume. The spring tension piston 55 compensates this loss of volume,however, performs a small subsequent stroke. Finally, the closer springtension piston 55 does not exactly stop at the desired position. Theassembly shown in FIG. 19 reduces this rebound by pumping the hydraulicoil, being actively pre-pressurized, from the closer springaccommodating space 92 through the third check valve 68 into the lockcompartment 61 during the opening process. Therewith, a relative openingresistance, similar to an opening damping, is intentionally generated inorder to bias the hydraulic oil and to obviate thecompression-set-behaviour. By virtue of the fourth check valve 69, thehydraulic oil cannot escape from the closer spring accommodating space92 toward the tank line T. Thus, the hydraulic oil is biased in thecloser spring accommodating space 92 by the closer spring tension piston55 during the opening process and flows into the lock room 61 with aspecific pre-pressure. Therewith, the undesired rebound is considerablyreduced.

Further, the following components and preferred specifications areprovided according to the invention:

Preferably, it is provided that the free-swing assembly is formed as asliding-coupling that exclusively transmits compressive forces betweenthe closer spring and the piston assembly. For the free-swing-function,no fixed connection may exist between the closer spring and the pistonassembly. Therefore, a sliding connection is preferably used, whichexclusively transmits compressive forces.

Preferably, the free-swing assembly is arranged between the piston rodand the piston assembly. As an alternative, the free-swing assembly ispreferably arranged in the piston rod or between the piston rod and thecloser spring, in particular between the piston rod and the closerspring tension piston.

Further, it is advantageous that the free-swing assembly comprises afirst front face arranged vertically with respect to the longitudinaldoor closer axis and being fixedly connected to the piston rod as wellas a second front face in parallel with the first front face and fixedlyconnected to the piston assembly, wherein the second front face liftsoff from the first front face and thus decouples when the closer springis locked. By two abutting and lifting front faces, a very simple andefficient free-swing assembly can be realized as a sliding-coupling.

Advantageously, a pocket is formed in the piston assembly, wherein thepiston rod is guided movably within the pocket. As an alternative, thepocket can also be formed in the spring tension piston. In a furtheralternative solution, the piston rod is formed of two parts, wherein, inthis case, the one part of the piston rod comprises a pocket openingtoward the longitudinal door closer axis and the other part of thepiston rod is disposed in this pocket to be movable in a translationaldirection.

Preferably, the door closer comprises an additional piston guided in thedoor closer housing between the piston assembly and the piston rod andfixedly connected to the piston rod, wherein the first front face isformed at the additional piston. The piston rod and the additionalpiston are fixedly connected, i.e. they always move together along thelongitudinal door closer axis.

In a preferred embodiment of the additional piston, it is provided thatthe connection between the piston rod and the additional piston isformed pivotally about a first axis perpendicular to the longitudinaldoor closer axis. Due to this pivotal arrangement, possible forces,which do not extend linearly to the longitudinal door closer axis andcould therefore result in a seizure, are prevented.

In addition, it is preferably provided that the connection between thepiston rod and the closer spring tension piston is formed pivotallyabout a second axis perpendicular to the longitudinal door closer axisand the first axis. Also due to this pivotal connection between thepiston rod and the closer spring tension piston, a possible seizure isprevented.

In case of a non-locked state of the lock compartment, the closer springcan act on the piston assembly through its biasing force via the pistonrod in direct pressure contact inside the free-swing-coupling, or in theopposite direction, the piston assembly may act on the piston rod. Inthis state, a normal door closer operation exists, in which the closerspring is manually tensioned and, upon release of the door, the closerspring moves the door back into the initial position through the pistonassembly and the output shaft. In case, however, the closer spring ishydraulically arrested, e.g. by energizing a solenoid valve, thehydraulic oil can no longer flow from the lock compartment.Consequently, the spring force can no longer act on the piston assembly,after the closer spring was manually tensioned once. When the door ismanually moved from the open position back into the direction ofclosing, the piston rod within the free-swing assembly, in particularwithin the sliding-coupling, lifts from the piston assembly. The pistonassembly itself moves, driven by the door and the output shaft, andperforms a small stroke. Inside the free-swing assembly, a distancebetween the first front face and the second front face is generated,which distance corresponds to the stroke. The returning motion of thepiston assembly due to another opening of the door occurs without force,which corresponds to a free-swing-function. Further manual opening andclosing motions of the door occur upon a still locked lock compartmentas often as desired and without force in the free-swing-mode. Only uponrelease of the lock compartment, the closer spring can be restored to areleased state. In this case, the first front face is brought intoabutment with the second front face in the free-swing assembly and theforce of the closer spring is transmitted to the door through the pistonassembly and the output shaft. Therewith, the door is securely closed bythe stored energy without any additional manual action being required.

In a preferred embodiment, it is provided that an additional closerspring is arranged between the piston assembly and the piston rod orbetween the piston assembly and the additional piston or between thepiston assembly and the separating wall, in order to load the pistonassembly slightly toward the closing direction when in free-swing-mode,wherein the additional closer spring is weaker than the closer spring.The closer spring fulfilling the fire protection function and beingconfigured very strong, is preferably tensioned once and then remainslocked via the lock compartment until a possible case of fire. For theeveryday use of the door, it is however also often desirable that thedoor closes after use, however, not with the force of a strong closerspring used for emergency cases. For this purpose, the additional weakercloser spring is used. In particular, this additional closer spring isconfigured according to EN1 or EN2 pursuant to DIN EN1154. A so-calledsecond pressure spring for a clearance compensation between the camroller of the opening piston and the rolling contour was alreadydescribed. Said second pressure spring is preferably replaced by theadditional closer spring. As an alternative, the use of piston assemblyinternal tie rods and clearance compensation springs can be combinedwith the additional closer spring.

Preferably, the door closer comprises a solenoid control valve, inparticular a 3/2-solenoid control valve. A closure damping compartmentis formed between the door closer housing and the piston assembly on aside of the piston assembly facing away from the piston rod, inparticular on the side of a damper piston. The solenoid control valvecontrols at least the pressures in the closure damping compartment andin the lock compartment. This solenoid control valve enables tohydraulically seal the lock compartment. Therewith, the closer spring,once biased, can no longer relax and the free-swing-function of the doorcloser is activated. By switching the solenoid control valve, the lockcompartment is again pressure-released and the closer spring candislocate the piston assembly and therewith close the door through theoutput shaft, e.g. in case of a fire.

In a preferred embodiment, it is provided that a first hydraulic line,in particular a pressure line P, extends from the lock compartment tothe solenoid control valve, a second hydraulic line, in particular anoperating line A, extends from the closure damping compartment to thesolenoid control valve, and a third hydraulic line, in particular a tankline T, extends from the solenoid control valve to a tank compartment.The hydraulic lines preferably extend substantially in parallel with thelongitudinal door closer axis and are integrated into the housing of thedoor closer.

In a preferred embodiment, an opening damping compartment is formedbetween the piston assembly and the separating wall and/or between thepiston assembly and the additional piston. A first throttled connectionis disposed between the opening damping compartment and the tankcompartment. The additional piston may be open-worked and does not haveto be guided sealingly in the door closer housing, such that the openingdamping compartment extends to the areas between the piston assembly andthe additional piston and between the additional piston and theseparating wall. Upon opening the door, the piston assembly dislocatesthe hydraulic oil from the opening damping compartment. The hydraulicoil flows through the first throttled connection, and in particularthrough the third line, into the tank compartment.

In a preferred embodiment of the opening damping compartment, it isprovided that a first unthrottled connection is arranged between theopening damping compartment and the tank compartment, wherein the firstthrottled connection is always open and the first unthrottled connectionis either closed or opened by the piston assembly, depending on theposition of the piston assembly. The first unthrottled connectionpreferably enters into the opening damping compartment between the firstthrottled connection and the output shaft. Therewith, the hydraulic oilcan be discharged through the first unthrottled connection into the tankcompartment at the beginning of the opening process of the door.Consequently, the door can be opened very easily and without anyresistance at the beginning of the opening process. When a specificopening angle is reached, the piston assembly, in particular the openingpiston, closes the first unthrottled connection. Consequently, thehydraulic oil can only be discharged through the first throttledconnection into the tank compartment and the door is damped shortlybefore it reaches its final position during opening.

Preferably, the door closer comprises a further throttled connectionwhich is arranged between the closure damping compartment and the tankcompartment, in particular in the third line. Said further throttledconnection serves for dampening the door in the closing direction.

In a preferred embodiment, it is provided that the solenoid controlvalve connects the first line to the third line and blocks the secondline in a first switching position; in a second switching position, thesecond line is connected to the third line and the first line isblocked. Therewith, the pressure line P and thus the lock compartmentare connected to the tank line T in the first switching position. Theoperating line A and thus the closure damping compartment are blocked.In this switching position, the closer spring or the closer springtension piston, respectively, are not locked and the free-swing-functionis deactivated. By blocking the operating line A, the hydraulic oil canbe discharged from the closure damping compartment into the tankcompartment only through the further throttled connection and theclosing process of the door is therewith always damped. In the secondswitching position, the pressure line P of the lock compartment isblocked and the operating line A of the closure damping compartment isconnected to the tank line. Therewith, the closure spring ishydraulically arrested and the free-swing-function is activated. In thisswitching position, the closure spring cannot transmit any force to thepiston assembly. Simultaneously, the closer dampening is deactivated andthe piston assembly is freely movable and the door can be moved withouta large effort. This embodiment of the hydraulic control is thepreferred embodiment.

In an alternative hydraulic control, it is provided that the solenoidvalve connects the first line to the second line in a first switchingposition, and connects the second line to the third line and blocks thefirst line in a second switching position. Consequently, in the firstswitching position, the pressure line P of the lock compartment isconnected to the operating line A of the closure damping compartment. Insaid switching position, the closer spring relaxes and dislocates thehydraulic oil from the lock compartment. With the first switchingposition, the lock compartment is set to the same pressure level as theclosure damping compartment. Due to this addition of the dislocated oilvolumes, a very fail-safe regulation of the closing speed can beachieved. The oil of both spaces, i.e. the lock compartment and theclosure damping compartment, together flow into the tank compartmentthrough the further throttled connection of the closure dampingcompartment. In the second switching position, the pressure line P ofthe lock compartment is blocked, such that the free-swing-function isagain activated. The operating line A of the closure damping compartmentis connected to the tank line, such that the closure damping duringfree-swing is deactivated.

In a preferred embodiment, it is provided that the solenoid valvereleases the closer spring when de-energized and enables thefree-swing-function when energized. With thisdeenergize-to-trip-principle, it is guaranteed that the door alwayscloses securely by the energy stored in the closer spring in case of apower breakdown. This closing function always has priority for anemergency case and is regulated by law or industrial standards.

Preferably, it is provided that a spring-loaded check valve is arrangedbetween the lock compartment and a compartment becoming smaller duringthe opening process of the door. This space becoming smaller during theopening process is in particular the accommodating space for the closerspring. The spring-loaded check valve locks toward the space becomingsmaller. According to the invention, a hydraulic pressure is built upand maintained in the lock compartment, in order to arrest the closerspring. For a pressure generation in the lock compartment, all elasticmembers contained therein, e.g. seals, residue air or also the hydraulicoil itself, are compressed accordingly. This results in an undesiredloss of volume. The closer spring tension piston compensates for thisloss of volume, however, performs a small subsequent stroke. Thissubsequent stroke is transmitted to the piston rod and consequently tothe piston assembly, the output shaft and the door. This results in aturning back of the door by several degrees. The door cannot be openedcompletely to the desired position during the free-swing mode. Thisundesired effect is referred to as rebound, which becomes noticeable inparticular in case of restricted door opening angles determined bystructural conditions. This effect is especially pronounced in case ofdoor closers with cam technology due to the small rotaryangle-stroke-ratio. The arrangement proposed herein, including thespring-loaded check valve, reduces said rebound by pumping the hydraulicoil, being actively pre-pressurized, from a pressure compartmentbecoming smaller in the opening direction through the third check valveinto the lock compartment during the opening process. Therewith, arelative opening resistance, similar to a opening damping, isintentionally generated in order to bias the hydraulic oil and toobviate compression-set-characteristics. In pre-known arrangements, thehydraulic oil is only passively suctioned from the tank compartment intothe pressure compartments during the opening process, which maypartially even generate a slightly negative pressure. The elasticmembers therewith completely relax and require a relatively highcompensation volume including a corresponding subsequent stroke in orderto enable again a holding pressure sufficient for the spring force. Inthis case, a maximum pressure difference exists. In the case describedherein, the compression-set-characteristics of the elastic members inthe lock compartment therefore occur during a slight pressuredifference, as a result of which the loss of volume and thus thesubsequent stroke is smaller. Accordingly, the turning back or therebound of the piston assembly from the intended position isconsiderably smaller.

Preferably, the check valve is arranged such that the hydraulic oil inthe space becoming smaller is pre-pressurized by the opening process andis thus actively pumped through the check valve into the lockcompartment.

Preferably, the check valve is arranged in the closer spring tensionpiston.

Further, it is advantageous that the space becoming smaller is closed,except for the check valve, during the opening process.

This closing is in particular achieved by arranging a further checkvalve between the space becoming smaller and the tank line, wherein thefurther check valve locks toward the tank line. Therewith, hydraulic oile.g. present in the accommodating space of the closer spring is biasedduring the opening process and can be pumped into the lock compartmentthrough the spring-loaded check valve in the closer spring tensionpiston.

The invention further comprises a hydraulic solenoid control valve, inparticular a hydraulic 3/2-solenoid control valve, comprising a valvehousing, a solenoid and a valve spindle. A valve chamber is integratedinto the housing. This valve chamber comprises a first valve seat boreas a connection to a first line, in particular a pressure line, a secondvalve seat bore as a connection to a second line, in particular anoperating line, and a free aperture to a third line, in particular atank line. The aperture is referred to as “free”, since it connects thevalve chamber to the third line in any switching position of the valve.The valve spindle is at least partially arranged within the valvechamber and is linearly moved by the solenoid. Further, the valvespindle comprises, within the valve chamber, a first sealing surfacefacing the first valve seat bore and a second sealing surface facing thesecond valve seat bore, such that selectively the first valve seat boreor the second valve seat bore can be closed. In addition, the valvespindle protrudes from the valve chamber through the second valve seatbore and through the second line toward the solenoid. Due to theprotrusion of the valve spindle from the valve chamber, the valvespindle can be connected to the solenoid or can be partially integratedinto the solenoid. In case the second valve seat bore is closed, thevalve spindle is pulled into the second valve seat bore by adifferential-area-ratio through the pressure of the second line, inparticular the operating line. This arrangement including a differentialarea ratio promotes a sealing of the second valve seat bore free ofleakage oil.

This differential-area-ratio is in particular achieved in that a sealingdiameter of the valve spindle outside the valve chamber is larger than adiameter of the second valve seat bore. The sealing diameter is definedat a seal between the valve spindle and the solenoid.

Preferably, the differential-area-ratio is obtained by configuring thediameter of the valve spindle outside the valve chamber to be largerthan the bore diameter of the second valve seat bore. Therewith, thepressure of the second line in front of the valve chamber can supportthe force of the pressure spring, when the second valve seat bore isclosed, and pull the second sealing surface into the second valve seatbore.

In a further preferred embodiment, the valve spindle consists of atleast two parts. For this purpose, the valve spindle comprises a firstpart and a second part, wherein the first part is guided to be linearlymovable in the solenoid and the second part is screwed into the firstpart. Consequently, the second part is fixedly connected to the firstpart and is linearly movable together with the first part. In particularfor providing the differential-area-ratio, this two-part form of thevalve spindle is especially easy to assemble. Therewith, in particularthe sealing diameter can be configured to be larger than the borediameter of the second valve seat bore.

In addition, it is preferably provided that a seal, in particular agroove ring seal, is arranged between the valve spindle and an armaturespace of the solenoid. Said seal is disposed at the already discussedsealing diameter between the valve spindle and the solenoid.Particularly preferred, the armature space is always freely connected tothe third line, in particular the tank line, via a connection channelextending through the valve spindle. Therewith, a pressure generation inthe armature space upon a possible leakage of the groove ring seal isprevented. The connection channel within the valve spindle extends fromthe armature space through the valve spindle into the valve chamber. Asalready described, the valve chamber is always freely connected to thethird line, in particular the tank line.

As an alternative to the afore-described hydraulic solenoid valve, theinvention comprises a hydraulic solenoid control valve, in particular ahydraulic 3/2-solenoid control valve, comprising a valve housing, avalve chamber integrated into the valve housing and including a firstvalve seat bore as a connection to a first line, in particular apressure line, a free aperture to a second line, in particular anoperating line, and a second valve seat bore as a connection to a thirdline, in particular a tank line. Further, this hydraulic controlsolenoid valve comprises a solenoid and a valve spindle moved by saidsolenoid and partially arranged in the valve chamber. The valve spindlecomprises, within the valve chamber, a first sealing surface facing thefirst valve seat bore and a second sealing surface facing the secondvalve seat bore, such that selectively the first valve seat bore or thesecond valve seat bore can be closed. Further, the valve spindle extendsfrom the valve chamber through the second valve seat bore toward thesolenoid.

In a preferred embodiment of the alternative hydraulic solenoid valve,it is provided that a connection of the third line to an armature spaceof the solenoid exists along the valve spindle or inside the valvespindle, such that a pressure generation in the armature space isprevented. In particular, this connection is realized by configuring aflat surface at the valve spindle, or by manufacturing the valve spindleas a polygon, in particular a hexagon.

In the following, advantageous embodiments of the two inventivehydraulic solenoid valves are described:

In a preferred embodiment, it is provided that the diameter of the firstvalve seat bore is smaller than a diameter of the second valve seatbore.

In a preferred embodiment, a pressure spring is arranged between thefirst valve seat bore and the valve spindle. In the variant including aball, the inventive valve may therefore be referred to as aspring-loaded ball-cone-seat valve.

In a further preferred embodiment, it is provided that the secondsealing surface, in particular the cone surface, seals the second valveseat bore in a de-energized state of the solenoid, and that the firstsealing surface, in particular the convex surface, seals the first valveseat bore in an energized state of the solenoid. The preferably providedpressure spring serves to press the second sealing surface of the valvespindle into the second valve seat bore in a de-energized state.

Preferably, the first sealing surface comprises a convex surface, inparticular a ball. Further preferably, the second sealing surfacecomprises a cone surface, in particular a cone ring surface. By linearlydisplacing or moving the valve spindle, the first valve seat bore isclosed by the convex surface or the second valve seat bore is closed bythe cone surface, selectively. A seizure in the switching position underpressure is effectively prevented by the ball valve embodiment includingthe convex surface.

Further, the invention preferably comprises a filter, in particular inthe first line. Particularly preferred, the filter is arranged outsidethe valve chamber directly in front of the inlet into the first valveseat bore. The filter prevents pollution of the oil and in particular apollution of the two valve seats. In a further preferred embodiment, thefirst valve seat bore is arranged directly opposite to the second valveseat bore. In a preferred embodiment, the solenoid comprises a coil, anarmature, a pole core as well as a gap between the pole core and thearmature. The pole core comprises a borehole along the longitudinal axisof the valve spindle and therefore provides an accommodation and alinear guidance for the valve spindle. Further preferably, the inventivesolenoid valves comprise a control unit for the solenoid. By saidcontrol unit, the solenoid can be switched between energized andde-energized.

Further, the invention comprises a hydraulic cartridge solenoid controlvalve, in particular a hydraulic cartridge 3/2-solenoid control valve,comprising one of the afore-described hydraulic solenoid valves, whereinthe housing is configured to be at least partially inserted into a valveadapter. Said valve adapter is located in a component which integrallyaccommodates the cartridge 3/2-solenoid control valve. Particularlypreferred, the first line, in particular the pressure line, and thesecond line, in particular the operating line, are directed radially orvertically outwardly with respect to the longitudinal axis of the valvespindle. In addition, O-ring seals are preferably arranged laterally ofthe outwardly directed first and second lines on the surface of thevalve housing, such that these lines can be connected pressure-tight byinserting the cartridge housing. Particularly preferred, the valvehousing comprises circumferentially extending ring channels for thispurpose. Starting at these ring channels, a plurality of radiallydirected channels for the first line and/or a plurality of radiallydirected channels for the second line may preferably lead to the valvechamber.

Further, it is preferred that the hydraulic cartridge solenoid controlvalve comprises a volume compensation unit including a tank compartment.This volume compensation unit including a tank compartment is integratedinto the valve housing or connected to the valve housing by a flange.The tank compartment is preferably connected to the third line. Thevalve is preferably structured along the longitudinal axis of the valvespindle as follows: The valve chamber including the valve spindle isarranged in the center. On one side of the chamber, the volumecompensation unit including the tank compartment is integrated orconnected by a flange. On the other side of the valve chamber, thesolenoid is mounted. Therewith, the hydraulic cartridge solenoid controlvalve can be inserted into a component with the volume compensation unitto the fore. The solenoid and in particular a plug at the solenoidpreferably protrude from the component. In a preferred embodiment, thetank compartment of the volume compensation unit is slightlypressure-loaded by a volume compensation piston and a compensationspring/pressure spring.

In addition, the invention comprises a door closer, in particular ahinge door closer, including a free-swing-function, comprising one ofthe afore-described hydraulic solenoid valves or one of the hydrauliccartridge solenoid valves, wherein the valve adapter is formed in thedoor closer. The hydraulic solenoid valve or the cartridge solenoidvalve is thus integrated into the housing of the door closer orconnected thereto by a flange, and serves to control the hydraulicbetween the closure damping compartment, the lock compartment and thetank compartment or the tank line.

The door closer including the hydraulic solenoid control valve furthercomprises preferably a door closer housing, an output shaft to beconnected to a door, a piston assembly connected to the output shaft andguided within the door closer housing, a closer spring, a piston rodarranged to connect the piston assembly and the closer spring, afree-swing assembly configured to enable a translational motion of thepiston assemblies de-coupled from the closer spring when the closerspring is locked, and a hydraulic lock compartment configured to lockthe closer spring.

The afore-described advantageous embodiments of the inventive doorcloser are accordingly preferably applied in the door closer includingthe hydraulic solenoid control valve or the hydraulic cartridge solenoidcontrol valve.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1.-15. (canceled)
 16. A door closer having a free-swing function,comprising: a door closer housing; an output shaft configured to beconnected to a door that comprises a cam-shaped rolling contourconfigured as a cam disc; a piston assembly connected to the outputshaft and guided in the door closer housing that comprises at least onecam roller and abuts on the rolling contour; a closer spring; a pistonrod that connects the piston assembly to the closer spring; a free-swingassembly for translational motion of the piston assembly decoupled fromthe closer spring when the closer spring is locked; and a hydraulic lockcompartment configured to lock the closer spring; wherein the outputshaft, and the piston assembly.
 17. The door closer of claim 16, furthercomprising: a fluid-tight separating wall arranged in the door closerhousing between the piston assembly and the closer spring, wherein thepiston rod passes through the separating wall in a fluid-tight manner.18. The door closer of claim 17, further comprising: a closer springtension piston guided in the door closer housing and abutting on thecloser spring.
 19. The door closer of claim 18, wherein the lockcompartment is formed between the separating wall and the closer springtension piston.
 20. The door closer of one of claim 17, wherein thepiston assembly comprises: a damper piston including a first cam roller;and an opening piston including a second cam roller, wherein the outputshaft is arranged between the damper piston and the opening piston. 21.The door closer of claim 20, wherein the damper piston and the openingpiston are connected via at least one tie rod.
 22. The door closer ofclaim 21, wherein the damper piston and the opening piston are connectedvia four tie rods.
 23. The door closer of claim 22, wherein respectivelytwo of the tie rods are arranged symmetrically with respect to alongitudinal door closer axis.
 24. The door closer of claim 22, whereintwo tie rods are arranged above the rolling contour and on both sides ofthe output shaft, and two further tie rods are arranged below therolling contour and on both sides of the output shaft, such that anoverall height of the rolling contour is arranged between the two uppertie rods and the two lower tie rods.
 25. The door closer of claim 22,wherein the piston assembly comprises at least two integrated clearancecompensation springs, wherein at least two tie rods are arrangeddiagonally to each other and are tensile-loaded by the clearancecompensation springs to compensate for a clearance between the rollingcontour and the cam rollers.
 26. The door closer of claim 25, whereinthe clearance compensation springs are arranged in at least one of thedamper piston and the opening piston.
 27. The door closer of claim 26,wherein the tie rods protrude through the clearance compensationsprings, wherein the clearance compensation springs are formed aspressure springs and act against respective ends of the tie rods, suchthat the tie rods are tensile-loaded.
 28. The door closer of claim 20,wherein a first pressure spring is arranged between the damper pistonand the door closer housing, the first pressure spring is configured fora clearance compensation between the rolling contour and the first camroller.
 29. The door closer of claim 28, wherein a second pressurespring is arranged one of: between the opening piston and the pistonrod; between the opening piston and an additional piston connected tothe piston rod; and between the piston rod and the separating wall,wherein the second pressure spring is configured for a clearancecompensation between the rolling contour and the second cam roller. 30.The door closer of claim 29, wherein at least one of the first pressurespring and the second pressure spring is supported against a stationarywall.
 31. The door closer of claim 16, wherein the door closer is ahinge door closer.
 32. The door closer of claim 29, wherein at least oneof the first pressure spring and the second pressure spring is supportedagainst a stationary wall.